This invention relates to a new and improved method and apparatus for separating heavy metals in the free state from their associated ores. More specifically, this invention concerns a separating wheel having a unique, multi-step separating surface which contains the function of several wheels and eliminates the expense of ancillary components usually employed in these types of separating apparatus.
One type of device employing multi-wheel separating surfaces is disclosed in my U.S. Pat. Nos. 4,008,152 and 4,110,206. These devices provide a series of single wheel separators with a separating surface comprising a series of spiral grooves which wind inwardly from the wheel periphery to a central annulus. Raw ore is fed to the wheel and is formed into a slurry which travels along the grooves and separates into a metal fraction and a light ore fraction. After at least two wheel fractionations, the metal fraction has a sufficiently high grade which enables it to be usefully processed.
While these devices perform adequately, a lighter device having fewer moving parts and fewer components would be desirable in some instances; obviously, such a device would be less expensive to manufacture. Where a single wheel separator is used, it would be easier to physically handle because of fewer controls and adjustments and ease of monitoring separating effects on the ore.
Heretofore, the basic problem in using a single wheel separator has been the necessity of reworking a batch of ore after an initial separation. This is due to the inherent separating capacity of a wheel which tends to be low because there is a limit to the amount of raw ore which it can feasibly carry. Also, it is desirable to employ narrow and shallow grooves near the center of the wheel so that the light, coarse ore will be rejected and only the heavy metal will travel along the final length of groove. However, if too much ore is applied to the wheel, these narrow grooves become overloaded, blocked, etc., and the free flow of metal is impaired.